Simplify the following expression: $a = \dfrac{p}{6} - \dfrac{5p}{8}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $6$ and $8$ $\lcm(6, 8) = 24$ $ a = \dfrac{4}{4} \cdot \dfrac{p}{6} - \dfrac{3}{3} \cdot \dfrac{5p}{8} $ $a = \dfrac{4p}{24} - \dfrac{15p}{24}$ $a = \dfrac{4p -15p}{24}$ $a = \dfrac{-11p}{24}$